Gorbachev's Policies and the End of the Cold War

During the late 1980s, numerous events brought about the end of the Cold War, significantly affecting international relations and domestic politics in the United States. Key figures emerged from this era who played pivotal roles in redefining U.S. foreign policy. One such figure was Mikhail Gorbachev, whose policies of glasnost and perestroika aimed to reform the Soviet Union's economy and open up to the world. Which of the following actions by Gorbachev is considered most directly responsible for reducing Cold War tensions and facilitating the dissolution of the Soviet Union?